Add post status dropdown selection control and preview

[westonruter]

When opening a draft post in the Customizer, it would be ideal to be able to make changes and then publish the post from there. For example in a workflow to preview how changes to a title wraps: https://youtu.be/sXu2pA42J88

As part of this, we can also implement the Trash button (#137) alongside the post status dropdown.

[lukecarbis]

Should this also include Visibility? i.e. Password / Public / Private / Scheduled, etc?

[westonruter]

@lukecarbis yes. Future would be implied by a publish status and setting a future date #53/#56. Or rather, if the date is set in the future, the publish option would not be available but only future, and vice-versa.

[westonruter]

For post_status, there should be a new post_field partial that has the behavior of doing a refresh for every change. There should not be any selective refresh aspect for changes to this field.